This study was conducted to evaluate the usefulness of the PLATO instructional system to teach adult basic education and general educational development students basic mathematics and reading skills. The study was conducted with a control group of students who had no use of PLATO during an 18-month period, a second group of students who had less than 20 hours of PLATO in a given subject, and a third, experimental group who had more than 20 hours of PLATO instruction in a given subject. Results indicated that there was no difference in achievement levels among the three groups; that retention was perhaps somewhat better for the students who used PLATO, and that time spent in classes was much greater for the students who used PLATO. Although few conclusions could be drawn because of lack of control over the study and lack of appropriate use of the PLATO system, one possible conclusion is that mixing instructional methods, i.e., applying traditional instruction and PLATO instruction intermittently in the classes, was confusing to the students. This could account for increased time in classes for students who used the PLATO system without increasing achievement. (Author/KC)